A heat exchanger is a device which is normally formed of a plurality of parallel tubes. Typically, a fluid to be heated (or perhaps cooled) is delivered through a heat exchanger. The tubes are contacted on the exterior of the tubes with a fluid which adds heat or removes heat as required. The nest of tubes forms a bundle. There will be typically a set of end plates known as heads constructed and arranged at the opposite ends of the tubes to support the plurality of tubes. Typically, heat exchangers are installed and operated in continuous fashion. Continuous use is normally carried on for several months. However, it is necessary to interrupt the process and to clean the tubes. The tubes typically collect a residue on the inner surface which reduces the heat transfer capabilities of the tubes. The tubes are normally formed of metal which has a relatively high thermal conductivity. The material which may coat on the interior, however, will not have an equal thermal efficiency for transfer of heat flux. Therefore, the coating formed on the interior of the tubes is detrimental to continued operation. Worse than that, as it builds up, the tube becomes more inefficient. One way to counter act this is to raise the temperature differential. However, there are limits to this. For instance, the metal used in the tubes of the heat exchanger has a limited capacity for heat as a result of metallurgical considerations. For instance, a heat exchanger which might operate for twenty years when operated at one temperature might have a life of only two years when operated at a temperature 100.degree. higher. The fatigue phenomena involved in constant exposure to elevated temperature is regrettably increased with an increase in temperature.
A typical heat exchanger is formed with a set of 180.degree. bends or elbows at the ends of the respective tubes to enable the fluid to be heated to flow in a repetitive fashion through the heat exchanger. At the time of cleaning, the bends are removed. This exposes the parallel or lengthwise tubes for cleaning. Cleaning normally involves reinoval of the accumulated trash or coating material on the inside of the tubes. The tubes can be fairly long. If they were sufficiently short and the tubes were of relatively large diameter, this would ordinarily enable hand cleaning or at least cleaning with a straight rod or similar cleaning instrument. As exchanger designs have become better, there has been a tendency to increase the length of the tube as a result of increasing the width of the heat exchanger. The cleaning task is somewhat difficult because the long and relatively narrow tubes do not permit access. They can be cleaned by pumping water or perhaps chemically active solvents into the tubes. That is successful but it has limitations. Moreover, since a typical heat exchanger includes a very large number of tubes, it is necessary to undertake the cleaning in a repetitive fashion so that a large number of tubes can be cleaned.
The present apparatus is summarized as a structure which incorporates a continuously operated pump with a sump. The pump delivers the output through a valve which is switched to deliver water under pressure through a controllable orifice. That delivers the water under pressure to a control cabinet which includes a plurality of valves. The valves determine the delivery of the water under pressure. It is delivered through an output line to a ram. The ram cooperates with a lance which is aligned with individual tubes. The lance is directed in an X and Y pattern by a control mechanism to align with selected tubes. The lance is able to travel forwardly in the Z direction. It is constructed on a piston and cylinder mechanism which enables hydraulic control of lance insertion and retraction. When insertion occurs, the tip of the lance is placed in the particular tube to be cleaned. Hydraulic control enables rapid indexing of the lance to the left and right to align with the proper tube and to insert into that tube once alignment has been accomplished. The tip of the lance is profiled so that it forms a fairly quick but not perfect seal with the end of the tube. It is hollow to deliver liquid through the end of the lance into the tube. An optional air inlet is also provided through the lanced tip. A pressure surge is set up by timed operation of the pump in cooperation with the orifice. Moreover, this delivers a flow of water into the tube. By appropriate shock wave creation with a mix of air and water injected violently into the tube, the corrosion materials collecting on the inside of the tube are fractured and break away. There is a rapid flow of multiphase fluid through the tube. This rapid flow agitates the corrosive material with sufficient shock tremors that it is broken and will flake off the wall and thereby be flushed out the tube.